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C5515 on-chip ADC

seanhuang
Prodigy 110 points
Other Parts Discussed in Thread: TMS320C5515

I have read the TMS320C5515/05/VC05 DSP Successive Approximation Register (SAR) Analog-to-Digital Converter (ADC) users' guide. But I don't well understand the Multi channel operation of ADC. There are very little words to describe it on page 17.

Could you please explain it in more detail for me? If I use the Multi channel operation of ADC, how does it work?

Thanks

  • 0
    TI__Expert 8065 points

    Hi Seanhuang,

    Basically, when MULTICH bit =1, it discharges array after switching to new channel and performing a new conversion. So, it provide more time to sample the analog input. So, this mode could possibly improve measurements in cases where the ADC input has abrupt voltage changes such as when changing from one input channel to another.

    It does not automatically switch channel selection. You need to select a desired channel at every time.

    Peter Chung

     

  • 0 in reply to Peter Chung
    TI__Expert 8065 points

    Hi Seanhuang,

    Basically, when MULTICH bit =1, it discharges array after switching to new channel and performing a new conversion. So, it provide more time to sample the analog input. So, this mode could possibly improve measurements in cases where the ADC input has abrupt voltage changes such as when changing from one input channel to another.

    It does not automatically switch channel selection. You need to select a desired channel at every time.

    Peter Chung

  • 0 in reply to Peter Chung
    Prodigy 110 points

    Peter Chung said:

    Hi Seanhuang,

    Basically, when MULTICH bit =1, it discharges array after switching to new channel and performing a new conversion. So, it provide more time to sample the analog input. So, this mode could possibly improve measurements in cases where the ADC input has abrupt voltage changes such as when changing from one input channel to another.

    It does not automatically switch channel selection. You need to select a desired channel at every time.

    Peter Chung

    Hi Peter,

    Thank you for your reply.

    In my current application, there are three analog inputs to be measured, and the sampling rate is 10ksps. Due to the ultra-low power consumption requirement,  C5515 need run at the speed of 3MHz. If CPU is configured to do the ADC input channel selection, CPU has no time to do other things. Could I use DMA controller do the ADC channel selection?  According to the ADC user's guide, I have known that DMA can be configured for ADC receive. But I am not sure that DMA controller can write the ADC control register and configure the ADC channel selection.

    Thanks

    Sean

  • 0 in reply to seanhuang
    TI__Expert 8065 points

    Sean,

    DMA should be able to write a data to any SAR registers. I have not done what you are trying to do but I think it  is doable. I am not 100% sure about the DMA latency and timing since you run the device at 3MHz, but give it a try.

    As you may know that DMA2 supports SAR, so configure DMA2 channel 1 to write to the SAR control register based on the SAR event. Then configure DMA2 channel 0 to read the SAR data also based on the SAR event. So, two DMA channels will read and write almost the same time at every conversion.

     

    Good luck!

    Regards,

    Peter Chung